Final answer:
Paclitaxel is the chemotherapeutic drug that affects the mitotic spindle by stabilizing tubulin in the microtubules, leading to cell cycle arrest and cancer cell death.
Step-by-step explanation:
The chemotherapeutic used to affect the mitotic spindle is Paclitaxel (b). Paclitaxel acts by stabilizing tubulin in the microtubules, preventing their depolymerization, which inhibits the proper functioning of the spindle apparatus during cell division. This disruption halts the cell cycle during the mitotic phase, particularly anaphase and telophase, and can lead to the death of rapidly dividing cancer cells.